I purchased the Matrox Dock (HDMI version) to cut down on the number of cables feeding up through the wire collar in my desk. I configured it from a Macbook Pro Retina 13 via Thunderbolt to the following: LG display via HDMI; ethernet to a Time Capsule; USB to an external Iomega drive; and as an occasional USB interface to an iPhone. Upon initial setup, one power cycle of the Matrox got everything working. Unfortunately, over a couple of days of use, random problems came up with the USB connections (which were supposedly fixed with an update). Twice, when hooking up the iPhone, it locked up iTunes to the point of having to force quit. This was remedied by power cycling the Matrox, but the failure occurred again at random times. Also, the Iomega drive would not always mount when powered up. Again, powering down/up the Matrox fixed the problem -- until the next time. Apparently other users are not experiencing these issues, so maybe I got a dud. I ended up returning the Matrox and purchasing the Belkin Thunderbolt Dock from Apple. So far, it is working fine.
For those of you interested in comparing the two units, here's my two cents. The Matrox felt more substantial and looked a bit nicer than the Belkin except I didn't like the way the Thunderbolt cable comes out of the front of the unit. With the Matrox, you will have cables coming out of both the front and the rear, whereas the Belkin gives you a choice -- all cables can hook up to the rear, but there's a channel cut out of the bottom that allows you to route a cable or two out the front. Also, the Belkin has two Thunderbolt ports, but the Matrox has one. Other than a slight aesthetic advantage to the Matrox chassis, I'd give the overall edge to the Belkin since it has worked flawlessly for me. The only negatives I see with the Belkin are the $50 price premium and the fact that it does not have an HDMI port, so I have to use a Thunderbolt-to-HDMI dongle (which adds even more cost).